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Engineering Controls Database

Punch Press 1 – Noise Case Study

Overview: The case history presented here is one of sixty-one case histories that were published by the National Institute for Occupational Safety and Health (NIOSH) in 1978 as part of an industrial noise control manual [NIOSH 1979]. The case histories are examples of engineering tasks that have been completed not only by professional noise control engineers but also by non-acoustical specialists who used common sense to solve their noise problems. The case histories were chosen primarily because the amount of noise reduction actually achieved was measured. Such engineering results, even if not directly applicable to a specific situation, illustrate general principles that may point the way to a successful result. They are intended to be useful to production and safety engineers, health personnel, and other factory personnel who are not specialists in noise control.

Case study: Two Minster model P2-2000, 200-ton straightside presses were running over 250 strokes/min when stamping out laminations for a particular motor model. The press is located in a metal construction building. Dies are changed often.
Sound level at the operator station was 104 dBA, and the general plant sound level was 92 dBA. The 104 dBA sound level only allows for 6 minutes of unprotected exposure before permanent damage is done. A worker can also only be exposed to 92 dBA of noise for 1.5 hours before permanent damage is done.

Hearing loss is one of the most common occupational diseases in America today and the second most self-reported occupational illness or injury. Approximately 30 million workers are exposed to hazardous noise on the job and there are approximately 16 million Americans with noise-induced hearing loss.
Panels forming a total enclosure were constructed with:

• 1 layer absorbent polyurethane acoustical foam
• 1 layer 1/64-in. sheet lead
• 1 layer 3-in. fiberglass blanket
• 1 layer fiberglass cloth to withstand industrial solvents.

The enclosure used was circular, 176 in. in diameter, 16 ft high, with a domed-top construction. Access doors allow for maintenance, and there is a stock feed opening. Finished parts leave the enclosure by means of two under-floor part guides. All supply lines were rerouted under floor, using flexible conduits. A 3500-cfm heat exhaust system with a silencer was added to each dome.

The operator is outside the enclosure except to change dies, change feed reels, or make adjustments.
NIOSH [1979]. Industrial noise control manual – revised edition. Cincinnati, OH: U.S. Department of Health Education and Welfare, Public Health Service, Center for Disease Control, National Institute for Occupational Safety and Health, DHEW (NIOSH) Publication No. 79-117.
noise control
noise control
punch press
punch press
Total enclosures reduced sound level for operator to 83 dBA and general plant sound level (with other equipment) to 87 dBA.